A known seat cushion adjusting apparatus is disclosed in JP2007-118706A (which is hereinbelow referred to as reference 1). The seat cushion adjusting apparatus according to reference 1 includes: a seat member, forming an outer shape of a seat cushion; a supporting member, supporting the seat member, and an adjusting member, engaged with an end portion of the seat member. The adjusting member is moved in a front-rear direction of a seat relative to the supporting member by a moving mechanism while being rotated around a rotational axis, extending in a width direction of the seat, by a rotational mechanism. Consequently, the end portion of the seat member is moved and an outer shape of the seat member is adjusted. Therefore, a length of the seat cushion (a seat surface) is adjusted so as to suitably support thighs of the occupant according to, for example, his/her physical size at the end portion of the seat member.
According to reference 1, along with a movement of the adjusting member in the front-rear direction of the seat, a guiding pin, fixed at the adjusting member, slides along a guiding hole of a guiding bracket, fixed at the supporting member, and thereby the adjusting member is rotated. Because of a high sliding resistance, an operation force for rotating the adjusting member is increased. For example, high torque is required for an electric motor, functioning as a driving source. Further, strength, (rigidness) of the guiding bracket, at which the guiding hole is formed, needs to be maintained and accordingly the guiding bracket is enlarged by, for example, increasing a thickness thereof.
An X-link moving mechanism is disclosed in a modified embodiment (a second embodiment) of reference 1. In the X-link moving mechanism, in order to elongate a moving distance of the adjusting member in the front-rear direction of the seat relative to the supporting member, each lever (a bar) of the link mechanism needs to be elongated and therefore, the moving mechanism is enlarged. Further, the operation force for rotating the adjusting member is increased because of the high sliding resistance between the guiding pin and the guiding hole.
A need thus exits for a seat cushion adjusting apparatus that is not susceptible to the drawback mentioned above.